INDUCTION OF DIAPAUSE IN AN ESTUARINE COPEPOD: HERITABILITY AND FLEXIBILITY OF PHENOTYPES

Northern populations of Acartia hudsonica may be present in the plankton throughout the year. To the south, however, populations spend the summer as dormant eggs in the sediments. Such differences may be genetic or phenotypic. I assessed the importance of these sources of variation in two populations using a full-sib rearing design and analysis of variance. Both populations showed significant sibship-environment interactions, indicating plasticity of phenotypes in the percentage of dormant eggs produced. Both populations also showed significant genetic variation with heritabilities approaching 1 in some experimental conditions.